1. Field of the Invention
The present invention relates to a flat light source apparatus for a liquid crystal backlight module.
2. Description of Related Art
An apparatus of light source is widely used in daily life. Conventional apparatus of light source such as a bulb using a filament conducted to generate a high temperature to produce a visible light source. This kind of bulb is basically a point light source. Then, a tubular light source is developed. After a long time of development and changes, a flat light source apparatus is also provided, for example, widely used in a flat panel display.
A plurality of mechanisms can be used to generate a light source. FIG. 1 is a schematic cross-sectional view of a conventional flat light source apparatus mechanism. Referring to FIG. 1, the light emitting mechanism is connected to a power source 106 through two electrode structures 100 and 102 to generate an electric field under an operating voltage, and uses a gas to discharge, which is also referred to as plasma discharge, so as to ionize a gas 104 to produce electrons 110. The electrons 110 are accelerated by the electric field to hit fluorescent layers 108a, 108b, and 108c respectively corresponding to red, green, and blue on the electrode structure 102. A visible light 112 is produced and emitted through the effect of the fluorescent layers. Herein, the electrode structure 100 is a light exit surface, which is usually a light transmissive material composed of a glass substrate and an indium tin oxide (ITO) transparent conductive layer.
Another light generating mechanism is a field-emission mechanism as shown in FIG. 2. FIG. 2 is a schematic cross-sectional view of another conventional flat light source apparatus mechanism. The conventional flat light source apparatus includes a glass substrate 120, a cathode structure layer 122, a plurality of conical conductors 124, a gate layer 126, an anode structure layer 128, and a fluorescent layer 130. The cathode structure layer 122 is disposed on the glass substrate 120. The plurality of conical conductors 124 is disposed on the cathode structure layer 122. A gate layer 126 is disposed on the conical conductors 124. A plurality of holes corresponding to the conical conductors 124 is provided on the gate layer 126. The anode structure layer 128 has a transparent anode layer disposed on a glass substrate. Moreover, the fluorescent layer 130 is disposed on the anode structure layer 128. Under the high electric field between the anode and the cathode, the electrons 132 are escaped from the top of the conical conductor 124, and after being accelerated by the electric field, hit the fluorescent layer 130 to emit a visible light.
The above two conventional light emitting mechanisms have their own advantages and disadvantages. The gas discharge mechanism can be easily achieved and has a simple structure, but is power-consuming since plasma is needed to be generated in the process. The field-emission light source is one of cold light sources, and is similar to a cathode ray tube (CRT) in principle, in which the high electric field between anode and cathode force the electrons to escape and hit the fluorescent powder coated on the anode so as to emit light. This light source is advantageous in high brightness and low power consumption, and can be easily fabricated into a flat structure. However, it is disadvantageous that a uniform emission material must be grown or coated on the cathode, for example, a spindle structure must be formed or a carbon nanotube is used. This flat fluorescent lamp needs a support to separate the anode and the cathode, and a vertical distance between the anode and the cathode must be adjusted carefully. Due to a small error tolerance, costs of a great number of structure designs and the yield must be taken into consideration in mass application, and the uniformity of the overall light emitting brightness is also difficult to control. Moreover, the vacuum packaging is also one of the problems.